Tubing and annulus pressure responsive and retrievable valve

Claim 1

IN COMBINATION WITH A WELL TUBING STRING, A RETRIEVABLE ASSEMBLY OPERABLE TO CONTROL THE UPWARD FLOW OF WELL FLUID IN SAID STRING, COMPRISING MEANS INCLUDING A TUBULAR BODY SIZED TO BE RUN VERTICALLY IN THE TUBING AND TO BE LANDED AT A PREDETERMINED LOCATION THEREIN, SAID MEANS FORMING FLOW PORTING AND AN ANNULAR SEAT EXTENDING ABOUT SAID PORTING, A BALL PLUG CARRIED BY SAID MEANS FOR MOVEMENT RELATIVE TO SAID SEAT TO CONTROL SAID UPWARD FLOW, SAID BODY HAVING A SIDE OPENING SIZE TO PASS THE BALL PLUG DURING SAID MOVEMENT AND THE BODY BEING MOVABLE VERTICALLY RELATIVE TO THE STRING DURING SAID BALL PLUG MOVEMENT, AND SAID MEANS INCLUDING ACTUATOR PISTON SURFACES CARRIED TO RECEIVE FLUID PRESSURE APPLICATION FOR EFFECTING SAID BODY MOVEMENT, THE TUBING STRING HAVING PORTING TO COMMUNICATE FLUID PRESSURE APPLIED FROM THE STRING EXTERIOR TO AN ACTUATOR PISTON SURFACE FACING IN ONE VERTICAL DIRECTION, ANOTHER PISTON SURFACE FACING IN THE OPPOSITE VERTICAL DIRECTION BEING OUT OF COMMUNICATION WITH SAID STRING PORTION BUT IN COMMUNICATION WITH THE STRING INTERIOR TO RECEIVE APPLICATION OF STRING INTERIOR FLUID PRESSURE, SAID SURFACES SIZED FOR RESPONDING TO A DECREASE IN SAID INTERIOR